Metal or more generally conductive housings for laptops and tablets, etc. are becoming fashionable. Generally, these metal or more generally conductive housings provide an elegant look and mechanical strength to a computer design. However it makes the antenna problem challenging.
Typical antenna designs like Monopole, Inverted F Antenna (IFA), or Planar IFA (PIFA) each require certain height or a certain distance from an electrical ground to provide adequate bandwidth and radiate efficiently. When coupled with a conductive housing, the desired height and distance may not be possible.
A slot antenna typically includes a metal surface, usually a flat plate, with a hole or slot cut out. When the plate is driven as an antenna by a driving frequency, the slot radiates electromagnetic waves in similar way to a dipole antenna. Generally, the shape and size of the slot, as well as the driving frequency, determine the radiation distribution pattern. However, in order to act as an antenna for modern networking frequencies (e.g., cellular, wireless local area network (WLAN or Wi-Fi), etc.), a slot antenna traditionally requires a very wide slot (e.g., greater than 6-7 mm). Alternatively, a slot antenna with a smaller slot would traditionally lack the desired bandwidth or radiating frequencies. Both these deficiencies limit practical application of a slot antenna within a conductive housing.